Hydrocarbon oils, such as crude oil and its distillation and conversion products, contain various contaminants that adversely impact refining processes. Crude oils and distillate oils may contain elemental metal or metal oxides and sulfides, particularly in the form of particulates which may originate in the crude oil itself or result from erosion or corrosion of metal piping or storage vessels. These metals may be harmful to downstream processes, such as catalytic cracking, and may poisoning cracking catalysts.
When deposited on cracking catalysts, metals can cause production of excessive amounts of coke and gas at the expense of desired fractions, such as gasoline and heating oil. Iron is a particularly detrimental contaminant, not only in catalytic cracking, but also in other catalytic processes such as hydrocracking.
It is desired to reduce the level of iron contamination in hydrocarbon feedstocks such as crude oils and distillate oils.
U.S. Pat. No. 3,463,339 discloses removal of soluble iron contaminants from hydrocarbon oils by treatment with aqueous sulfuric acid, followed by separating the iron-free oil from the aqueous acid phase to which the iron has been transferred.
U.S. Pat. No. 3,459,658 discloses removal of iron contaminants from hydrocarbon oils by contacting iron-contaminated oil with an aqueous medium containing an acid and a reducing agent capable of reducing iron from the ferric to the ferrous state.
U.S. Pat. No. 5,271,863 discloses removal of soluble iron contaminants from hydrocarbon oils by contact with a Mannich reaction product, which forms a complex with the iron species.
Related to iron contamination of hydrocarbon oils, aqueous liquids that may be used or generated in oil and gas drilling and recovery can contain substantial amounts of iron of geologic origin.
Flowback water is a water-based solution that flows back to the surface during and after the completion of hydraulic fracturing or “hydrofracking”. It consists of the fluid used to fracture the shale. The flowback consists of 20 to 40% of the volume of hydrofracturing fluid that was initially injected into the well. The remainder of the fluid remains confined in the shale formation. The hydrofracturing fluid, through its injection and return to the surface in the form of flowback water, travels through geologic formations and when recovered may contain a variety of formation materials, including salt, heavy metals and other pollutants, making it unsuitable for disposal in freshwater lakes, rivers and aquifers. In particular, flowback water may contain significant amounts of iron.
Produced water, also known as brine or “oilfield brine”, is naturally occurring water that is co-produced with the extraction of oil or gas from underground reservoirs. As reservoirs mature, the quantity of produced water climbs and often exceeds the volume of the hydrocarbons before the reservoir is exhausted. During gas extraction by hydrofracking, produced water is found in shale formations that flows to the surface throughout the lifespan of the gas well. At some point, the water that is recovered from a gas well makes a transition from flowback water to produced water.
Produced water, like flowback water, can contain significant amounts of iron from geological sources. What is needed is a method to reduce the concentration of iron contamination in flowback water and produced water, as well as in hydrocarbon oils.